Aythya marila


Taxonomy [top]

Kingdom Phylum Class Order Family

Scientific Name: Aythya marila
Species Authority: (Linnaeus, 1761)
Common Name(s):
English Greater Scaup, Scaup

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2012
Date Assessed: 2012-05-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): McCoy, T., Burfield, I., Ellermaa, M., Kontiokorpi, J., Kharitonov, S., Lehikoinen, A., Bianki, V., Kharitonova, I., Barclay, J., Lehikoinen, E., Szymanski, M. & DeVink, J.
Facilitator/Compiler(s): Butchart, S., Calvert, R., Derhé, M., Ekstrom, J., Malpas, L.
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Although the population may be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is extremely large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

Geographic Range [top]

Range Description: Summer breeding grounds of the Greater Scaup range across the northern limits of Europe (including Iceland) and Asia, through the Aleutian Islands (year-round breeding) to Alaska (USA), and across to the Atlantic coast of Canada (del Hoyo et al. 1992). It winters further south, reaching California, the great lakes and northern Florida in North America, the Adriatic Sea and northern Black Sea in Europe, the western Caspian Sea, and on the Pacific coast of Asia as far as south-east China (del Hoyo et al. 1992).

Albania; Antigua and Barbuda; Austria; Azerbaijan; Bahamas; Bangladesh; Belarus; Belgium; Bermuda; Bosnia and Herzegovina; Bulgaria; Canada; China; Costa Rica; Croatia; Cuba; Denmark; Estonia; Faroe Islands; Finland; France; Germany; Greece; Hungary; Iceland; India; Iran, Islamic Republic of; Iraq; Ireland; Italy; Japan; Kazakhstan; Korea, Democratic People's Republic of; Korea, Republic of; Latvia; Liechtenstein; Lithuania; Luxembourg; Macedonia, the former Yugoslav Republic of; Mexico; Montenegro; Myanmar; Nepal; Netherlands; Northern Mariana Islands; Norway; Pakistan; Philippines; Poland; Portugal; Puerto Rico; Romania; Russian Federation; Saint Pierre and Miquelon; Serbia (Serbia); Slovakia; Slovenia; Spain (Canary Is. - Vagrant); Sweden; Switzerland; Taiwan, Province of China; Turkey; Turkmenistan; Turks and Caicos Islands; Ukraine; United Kingdom; United States (Georgia - Present - Origin Uncertain); Viet Nam
Afghanistan; Algeria; Barbados; Cyprus; Gibraltar; Greenland; Hong Kong; Israel; Jamaica; Malta; Mongolia; Morocco; Svalbard and Jan Mayen; Tunisia; Virgin Islands, U.S.
Present - origin uncertain:
Egypt; Georgia; Guam
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: The global population is estimated to number c.1,200,000-1,400,000 individuals (Wetlands International 2006), while national population sizes have been estimated at c.50-1,000 individuals on migration and c.50-1,000 wintering individuals in Taiwan and c.1,000 wintering individuals in Korea (Brazil 2009).
For further information about this species, see 22680398_aythya_marila.pdf.
A PDF viewer such as Adobe Reader is required.
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: Behaviour This species is fully migratory (del Hoyo et al. 1992). It breeds in the high Arctic from late-May or early-June (depending on the timing of the Arctic thaw) (Kear 2005b) in single pairs or loose groups (del Hoyo et al. 1992), often with colonies of nesting gulls or terns (Kear 2005b) although it is not itself a colonial species (Snow and Perrins 1998). Males undergo short post-breeding moult migrations (Madge and Burn 1988, Scott and Rose 1996), often gathering in small or large flocks (up to 4,000 in Iceland) (Scott and Rose 1996) while females are incubating (Madge and Burn 1988). Females usually moult on the breeding grounds (Madge and Burn 1988, Scott and Rose 1996), although large concentrations (500-1,000 individuals) of moulting females have been recorded away from breeding areas (Scott and Rose 1996). During the moulting period the species is flightless for a period of c.3-4 weeks (Scott and Rose 1996). The autumn migration begins after the moulting period in mid-August (Scott and Rose 1996), with males tending to remain much further north than females or immatures (del Hoyo et al. 1992) leading to some sexual segregation during the winter ( Madge and Burn 1988). The species is highly gregarious outside of the breeding season (Kear 2005b) and is commonly observed in small or large flocks ( Madge and Burn 1988) sometimes of several thousand individuals (Scott and Rose 1996). The return spring migration generally begins in late-February (Scott and Rose 1996) although flocks of non-breeders may remain in the south, often in winter quarters, during the breeding season (Madge and Burn 1988). Habitat Breeding The species breeds in tundra (Kear 2005b), wooded tundra (Scott and Rose 1996) and moorland regions (Kear 2005b) in the high Arctic (del Hoyo et al. 1992), occupying small, shallow (del Hoyo et al. 1992), freshwater lakes, pools and rivers (Kear 2005b) with grassy shorelines and high densities of invertebrate life (Johnsgard 1978). It shows a preference for water less than 6 m deep (usually 2 m) for diving (Kear 2005b). Non-breeding The species winters on shallow coastal waters (del Hoyo et al. 1992, Kear 2005b) less than 10 m deep (Scott and Rose 1996) (especially in the vicinity of sewage outlets) (del Hoyo et al. 1992), as well as sheltered bays (del Hoyo et al. 1992), estuaries (del Hoyo et al. 1992, Kear 2005b) and brackish coastal lagoons (del Hoyo et al. 1992). It is also found inland on large lakes (Johnsgard 1978, del Hoyo et al. 1992, Kear 2005b) and reservoirs during this season (Madge and Burn 1988). Diet The species is omnivorous (Kear 2005b), its diet consisting predominantly of molluscs (e.g. mussels [Kear 2005b] Mytilus spp. [del Hoyo et al. 1992], cockles Cardium spp. and clams Macoma spp. in coastal habitats, and Hydrobia spp. in brackish habitats [Kear 2005b]) especially during the winter (Johnsgard 1978), as well as insects (del Hoyo et al. 1992), aquatic insect larvae (Johnsgard 1978), crustaceans (del Hoyo et al. 1992) (e.g. amphipods [Johnsgard 1978]), worms, small fish (del Hoyo et al. 1992), and the roots, seeds and vegetative parts of aquatic plants such as sedges (del Hoyo et al. 1992) (Kear 2005b) and water weeds (Kear 2005b). Breeding The nest is a shallow depression close to water (Madge and Burn 1988) on the ground (del Hoyo et al. 1992), either in thick vegetation (del Hoyo et al. 1992) (Kear 2005b), in cracks in rocks, under woody shrubs or under perennial herbaceous vegetation less than 50 cm high (Iceland) (Johnsgard 1978). The species is not colonial but it will sometimes nest among gulls and terns (Kear 2005b), with neighbouring nests being placed as close as 1 m in some areas (Snow and Perrins 1998). In Scotland, UK the introduction of a sewage treatment scheme in the Firth of Forth (a large marine bay) resulted in a considerable reduction in the abundance of the species, with feeding flocks only remaining at outfalls where sewage continued to be discharged in large quantities (Campbell 1984). It was unclear whether the changes in the species's distribution were due to reductions in the number of food items borne in the sewage or to reductions in aquatic invertebrate abundance as a result of the new treatment system (Campbell 1984).

Systems: Terrestrial; Freshwater; Marine

Threats [top]

Major Threat(s): The species is susceptible to oil pollution (Kirby et al. 1993, Kear 2005b) when moulting and in winter and may be threatened by high levels of organochloride contaminants (Kear 2005b). Its habit of congregating around coastal sewage outlets in the winter also puts it at risk from other pollution types (del Hoyo et al. 1992) and large numbers often drown due to entanglement in fishing nets (Kirby et al. 1993). The species is threatened by hunting for sport in North America (Schmidt 2006, Blohm et al. 2006), and suffers from disturbance from hunting (Evans and Day 2002). It is also susceptible to avian influenza, so may be threatened by future outbreaks of the virus (Melville and Shortridge 2006). The species is hunted legally for sport in seven countries of the European Union (Kear 2005b) (e.g. Denmark [Bregnballe et al. 2006]), and is hunted for commercial and recreational purposes in Iran (Balmaki and Barati 2006).

Conservation Actions [top]

Conservation Actions:

Citation: BirdLife International 2012. Aythya marila. The IUCN Red List of Threatened Species. Version 2015.2. <>. Downloaded on 29 August 2015.
Disclaimer: To make use of this information, please check the <Terms of Use>.
Feedback: If you see any errors or have any questions or suggestions on what is shown on this page, please provide us with feedback so that we can correct or extend the information provided